Global Navigation Satellite System (GNSS) based navigation is widely used in precision navigation and performance based navigation systems in vehicles, particularly aircraft. The GNSS receiver resolves the vehicle or aircraft position based on the position reference system (Geodetic Datum), that is generally interchangeable with service providers like European Geostationary Navigation Overlay Service (EGNOS), Global Navigation Satellite System (GLONASS), Wide Area Augmentation System (WAAS), et cetera. The most commonly used position reference is World Geodetic System (WGS-84) which is an Earth-centered, Earth-fixed terrestrial reference system and geodetic datum. Global Positioning Systems (GPS) use WGS-84 whereas GLONASS use Parametry Zemli 1990 (PZ-90). WGS-84 and PZ90 are interoperable.
The navigation database used with aircraft navigation systems like flight management systems (FMS) detail waypoints and their positions. These positions are either surveyed per WGS-84 or based on a nonstandard local reference, and the compliance information is available in the navigation database. Since GPS uses WGS-84, when operating in countries that do not use WGS-84 (e.g., Russia, China), pilots should exercise caution because the surveyed latitude & longitude of the airport and other navigation database references are not consistent with positions provided by the WGS-84 based GPS. The use of local radio aides stored in the navigation database will be consistent with the surveyed locations. Continuing with a GPS based navigation in geographical areas like this would lead to inaccurate GPS data.
It is critically important that an aircraft has accurate GPS data in order to make precision approaches during landing. The pilot should not engage GPS approaches to non-compliant airports since the databases in the aircraft are in WS-84 format. Currently, there is no mechanism to differentiate the WGS-84 airports from the non-compliant airports on the Multi-Function Display (MFD) of the aircraft. Lack of this differentiation or indication may lead to issues during landing such as deviations from the intended or desired approach path. On most aircraft, the pilot can manually deselect the GPS prior to the approach, if the compliance to WGS-84 is not known. It is recommended pilots do so prior to the approach so the system has time to acquire ground-based navigation and triangulate position in time for the arrival procedure. Procedures vary somewhat based on the avionics system and FMS software version.
Accordingly, it is desirable to provide a system and method for displaying portions of a route on a coverage map that are non-compliant for an GNSS navigation system in an aircraft. Furthermore, other desirable features and characteristics of the exemplary embodiments will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and the foregoing technical field and background.